How to reduce SF6 emissions
SF6 has been in use as an insulation medium since the 1960’s. It exhibits excellent properties allowing for more compact switchgear, transformers, and Gas-insulated Lines. While the lifespan is 30-50 years, SF6 is, unfortunately, a severe green-house gas with the high global warming potential (GWP) of 22,800, relative to CO2. It is therefore necessary to reduce emissions of SF6. This paper covers the work CIGRE is has done and is doing in this area. CIGRE’s experts are also involved in developments for alternative gases to SF6. Technical brochures and working groups relating to emissions and alternate gases are referenced for your information and can be downloaded from e-cigre.org.
Sulphur Hexafluoride (SF6) gas for high voltage insulation or current interruption provides solutions that are superior to all other known technologies for equipment such as Gas-insulated Switchgear (GIS), Gas Circuit Breakers (GCB), Gas-insulated Lines (GIL) and Gas-insulated Transformers (GIT) used in electrical power transmission and distribution networks and similar installations.
The use of SF6 in electrical equipment provides the significant advantage of reduced space requirements, especially in cities and offshore wind platforms where there is limited space and the cost of land is high and where space requirements are an important design consideration. Another positive aspect is that the conductor’s insulation prevents degradation due to extreme weather or other environmental conditions.
GIS have been widely used since the 1960’s and TB 513 covers over 20,000 units in 24 countries.
SF6 gas is colourless, odourless, non-toxic, non-flammable, and non-reactive gas under normal environmental conditions. It is also dense, about five times heavier than air, so safety requirements for its use are significant and staff need to be well trained in its use.
However, the GWP of SF6 alone is not an adequate measure of the environmental impact of electric power equipment based on this technology, given that any environmental impact of an application should be evaluated using Life Cycle Assessment (LCA).
In order to meet these environmental and safety demands, the focus for manufacturers and asset owners is on finding ways of increasing equipment tightness, reducing leakage and handling losses, management of reporting obligations, personnel training, labelling, and handling of SF6 electrical power equipment. CIGRE has discussed and published a variety of Technical Brochures to give guidelines related to those topics as follows:
- TB 234: SF6 recycling guide
- TB 430: SF6 tightness guide
- TB 594: Guide to minimise the use or loss of SF6 during routine testing of electrical equipment
- TB 723: SF6 measurement guide
Actions include:
- Compact equipment design which requires a smaller quantity of SF6; (this should be achieved with care – refer TB 571);
- Improving handling processes and handling equipment during commissioning, service, operation, and end-of-life, by following the recently reviewed IEC standards and CIGRE Technical Brochures;
- Application of SF6 recycling techniques;
- Trained and qualified personnel in all equipment stages and gas lifetime.
In addition to mitigation measures already recommended, CIGRE is looking to provide further contributions to reduce SF6 gas emission in the future and recently established the following Working Groups related to recent developments in alternative gases and vacuum solutions to support a sustainable society by reducing SF6 gas emissions in the future. The relevant Working Groups are:
- WG D1.51: Dielectric performance of eco-friendly gas-insulated systems
- WG D1.67: Dielectric performance of non-SF6 gases for gas-insulated systems
- WG A3.41: Interrupting and switching performance with SF6 free switching equipment
- WG B3.45: Application of non-SF6 gases or gas-mixtures in MV & HV gas-insulated switchgear